There are known vehicle occupant protection systems in which a control unit and satellite sensors are connected through bus lines (see, for example, published Japanese patent documents JP-A-2002-529292 and JP-A-2001-512395).
In the system disclosed in JP-A-2002-529292, the bus lines are connected in a ring configuration, whereas the bus lines are connected in a point-to-point and daisy chain configuration in the system disclosed in JP-A-2001-512395. The ring and point-to-point configurations have a complex bus line layout and require many cables, which leads to a cost increase. The daisy chain configuration has the advantage of lower cost, but on the other hand, a cable disconnection will disable all the satellite sensors downstream of the disconnected point of the cable. The technique in JP-A-2001-512395 therefore utilizes a combination of both the point-to-point and daisy chain configurations so as to reduce the disadvantages of the daisy chain.